Guilt
After spending the afternoon with Hinata, Gaara walks in to his house far later than usual; the full moon is shining brightly tonight. There is a picnic basket on the kitchen counter, he places the package of left-over cookies next to it.
He is surprised to find Sakura awake. She has a book in her hands, but she is not reading it. Instead, the village lights flicker in her eyes. He notices that she has caught the sun; petite shoulders are suddenly freckled and tinted pink. He hovers in the hall, fascinated with her sitting in the windowsill. It's almost as if she has been painted there; she is still and looks worried by something.
He wonders what it is; he has gone to lengths to make she she has everything she needs. She has her own clinic in the village; which he knew she loves. Hinata had told him how she had grown sick of healing - and more often, failing to heal - wounded nin from the war. He could understand why. The war had taken it's toll on medics more than anyone else.
He had also made sure that she had the run of the Kazekage Garden, for he remembered visiting Naruto and Ino's house once, the find the place covered in various plants all gifted from Sakura.
He gave no restraints on her freedom; and allowed her to come and go as she pleased. Though, she had never strayed outside the village gates.
He can still see her unhappiness etched in her face. Suddenly, he is overwhelmed with the feeling of wanting to comfort her - so he tries to. He walks across the hall and crouches beside her. She turns to him, eyes glistening with sadness and confusion. He has no idea what to say and it takes him a lifetime to find even a single word.
He finally settles on a heartfelt "Sorry."
She placed her head on the window and cries; the sight is enough to kill him. He touches her cheek gently and she turns picturesque again - still and painted. He whips around and leaves their home, weighed with guilt, and spends the night wrecking dunes in the desert.